My Mom's family has been making a similar recipe for at least three generations. Ours calls for 1.5C of butter to 2C of sugar (and no vanilla), so it yields not quite twice what author's recipe does.

I've screwed up plenty of batches in my years but it was never due to separation but rather burning the butter. Since I began doing it in a heavy-duty aluminum sauce pan (heavy on the sides and bottom, not just the bottom), I've not had any problems. I find I get more consistent results if I don't stir too much. I stir a lot at the start until the sugar is fully dissolved and the butter is fully melted, and again at the end, at about 275deg through the finished product to make sure it doesn't burn on the bottom. In between it only gets stirred a few times.

We give this as holiday gifts - my wife's family looks forward to it every year. Over the years I have modified the preparation to make what is in my opinion a more professional presentation.

I butter a jelly roll pan and cover it with around 3oz of slivered almonds. This goes 4" under the broiler (on low setting - our GE Profile range has two broiler temps) and the almonds get toasted for precisely 1min, 40sec. The pan comes out and goes onto a cooling rack.

The candy is cooked to hard crack, and poured over top of the toasted almonds. This is left to cool at room temp for exactly 7 minutes, just until it starts to set up. I then use a metal scraper to press-cut the candy into ~1.5inch squares. Once the candy is completely cooled, it comes right out of the pan with a spatula.

Once the candy squares have cooled all the way to room temp, I fill my double-boiler with a pound of chocolate (my preference is a 50/50 mix of milk and semisweet - Ghirardelli when I can get it) and a piece of paraffin that's about the size of your pinky. One by one, each toffee square is submerged in the melted chocolate and retrieved with a pair of tongs. Drain the excess chocolate for a few seconds and then carefully place the finished product on waxed paper to cool. This goes in the fridge for an hour or more to completely cool.

On chocolate: I've played with tempering chocolate by several methods, using really high-end chocolate, using special "melting chocolate", etc. In my hands, paraffin combined with a decent-quality chocolate is hands down the way to go. No fussing, no mess, no blooming, no sticky chocolate coating.

This method is more labor-intensive but the result is very professional, highly reproducible, and of course DELICIOUS). Having the chocolate completely covering the toffee allows you to keep the candy out, at room temperature, for at least a couple of weeks, with no ill effects though it doesn't usually last that long!

I used this recipe today and it worked exactly as described. It is moderately dry here because it's winter + our heat is on, but it isn't "southwest US" dry because I'm in Georgia. The temperature indoors is 71.

I followed the directions exactly, except I began on "2" out of 10 and only ever got as high as "4". I used 1/2 white and 1/2 brown sugar because of what I had on hand. I stirred regularly (i.e. about every 5 seconds) throughout the entire process, and on the whole it was about 10 minutes of cooking.

I did not have a candy thermometer (d'oh) so I knew I was going out on a limb, but I just took it off the heat after it was slightly browner than when I started and visibly quite thick. I forgot to add vanilla, but I didn't miss it in the final product. I didn't have any chocolate, so I sprinkled some dark cocoa over the hot toffee and it added just a little chocolate taste (but isn't necessary).

The only thing I would change next time is that I would have scored the hot toffee to make breaking easier. The thickest parts were quite difficult to break once it was cooled.

Yes, how high your kitchen is (in the geographic sense) has a great deal to do with candy making. I grew up and learned to cook on the East Coast. Now I live in Albuquerque (roughly 5,500 feet where I am). Water boils at 200 degrees, not 212 degrees as it does at sea level. This is not insurmountable if you use a candy thermometer and calibrate it as follows.

Place a pot of plain water on the stove, preferably the same pot you plan to cook the candy in or one similar. Set your candy thermometer in place and bring the water to boiling at a similar setting to what you plan to use. when the water boils vigorously (not a few bubbles here and there) note the temperature on your candy thermometer. Subtracting the temperature you get from 212 (sea level boiling point) gives you the correction you need to make in every recipe. Water boils at 200 degrees in my kitchen, so the correction factor is 12 degrees. If a recipe calls for 300 degrees, I know I should cook until 288 degrees (300-12) for the recipe to work for me.

For those engineers who are new to candy making, be aware that a glass candy thermometer must be placed so the bulb is fully in the boiling mixture, but NOT touching the bottom of the pan! The one I use has a glass tube in a metal housing that forms a step beneath the bulb, preventing the glass from hitting the pan.

What you can do if your batch fails. Make them into Chocolate Almond Cookies.

I've made a lot of batches, usually with success.

I recently tried to make a double bactch in a larger pot. I doubled the butter to 1 lb. and added 3 cups of sugar. In lieu of my usual corn syrup, I used a little maple syrup because it was leftover from breakfast.

The larger size required a larger pot. The batch went very granular on solidifying. The toffee base was very white in color. It was hard (not chewy) but definitely granular and definitely not toffee. It already had the chocolate and nuts on it. I decided to make use of all this good stuff and make cookies.

It required a little experimentation, making some dough and baking 1 cookie, adjusting, and baking more.

Here's the general recipe.

Take the failed batch and put it into the food processor, grind it up into a paste. This becomes your sugar/flavorings and more than half the butter for your cookies.

In the standing mixer with a paddle attachment, cream a small amount of unsalted, room temperature butter (half to 3/4 stick) until fluffy. Add in your paste a little at a time until incorporated. Add 1 egg and a little vanilla extract.

Toast some almonds, cool, and grind them up well in food processor with a little sea salt (to taste).

With a spoon, take some of the cool dough and roll into ball about 1 T to 1.5 T in size. Roll ball of dough in ground nuts. Place on parchment or silpat on cookie sheet and press down to flatten to about 3/4 inch thick.

Bake at 375 F for about 12-15 mins, rotating pan halfway through, until cookie is medium-browned around edges.

Cool on sheet on cooling rack for 2-4 mins to set and then carefully remove cookies to rack to cool further.

Experiment with more or less flour or butter to get the right consistency.

I started with just a portion of my aborted batch of toffee so that I could tweak it as I went along. Good Luck.

Absolutely fascinating! I Googled English toffee recipes, spotted this one as seeming to have a lot of useful detail, scrolled down and became entranced by the long technical discussions that followed, was terribly impressed by the continued experimentation and careful reporting of results, realized eventually "These are not normal cooks!" and only then discovered that I was reading "Cooking for Engineers."

Process employed and reactions observed: I heated butter, sugar and water together over very low flame, stirring occasionally. The mixture began to boil while still over low flame. I continued to stir occasionally. The mixture took on a thick, spongy texture as the temperature rose. Not trusting the candy thermometer, especially as the mixture began to clump and pull away from it, I used the cold water test (frequently dropping a small spoonful of mixture into cold water and observing its texture when cooled). Suddenly, shortly after the "firm ball" stage, it separated. I continued stirring and testing; "hard crack" was reached at the same time as the desired color change.

I poured off the separated fluid (clarified butter) and stirred in vanilla, whereupon further separation occurred and I poured again. Although it seemed to have "completely separated" I measured the fluid and it was only 1/3 cup, so either the butter was 2/3 water or some was incorporated into the toffee after all.

I continued as directed, with excellent results! It's delicious; the texture is perfect, crisp and not grainy; separation didn't set it back a bit. The only advice I can add to the wisdom already accumulated here is to just pour off the separated-out butter before spreading the toffee, and see what you get. (You may find a use for the clarified butter, too.)

It will be interesting to try more batches and mess with all the variables. I don't doubt that corn syrup helps, but my partner is seriously allergic to it.

Not exactly. With the amount of butter used in this recipe, there can be as much as 2 to 4 grams of salt (depending on the brand) contributed by the salted butter. That's actually a lot more than I call for in this recipe, so if you use salted butter, don't add anymore. The final result will be saltier than the recipe I present here, but you might like that. Personally, I'm a bit fan of savory sweets.

On another note, because of the huge differences between salt content in different brands (Kerrygold usually has only 1g salt per 4-oz weight stick while Horizon reported has as much as 2.3 g for the same stick), we like to use unsalted butter in our recipes so the result is as repeatable as possible when different people (with different brands of butter in different markets and regions) attempt the same recipe.

I have no experience as a chef or baker, or any kind of food preparation expert what so ever. I really love English toffee, though, and thought it might be fun if my girlfriend and I could try to make some. Is this a pretty easy thing to pull off, or is it easy to burn or mess up? Also, I live at around 7,000'. Will this be a factor?

I made my first batch of this toffee yesterday and it was perfect! Problem is, it didn't last through the evening - it just disappeared! I'm making another batch today and would like to know if I can freeze it, well wrapped, in an airtight container. I'd like to keep it until Christmas as I might not have much more time to make another batch. Any advice would be appreciated.

I made my first batch of this toffee yesterday and it was perfect! Problem is, it didn't last through the evening - it just disappeared! I'm making another batch today and would like to know if I can freeze it, well wrapped, in an airtight container. I'd like to keep it until Christmas as I might not have much more time to make another batch. Any advice would be appreciated.

I've kept toffee bagged or in an airtight container in the refrigerator for over a month without people complaining about a texture problem. To my taste, it isn't quite as good as serving the next day, but it seemed to be very good. I have not tried freezing yet.